Attenuated superactive multimetallic catalytic composite

ABSTRACT

A novel attenuated superactive multimetallic catalytic composite especially useful for converting hydrocarbons comprises a combination of a catalytically effective amount of a pyrolyzed rhenium carbonyl component with a porous carrier material containing a uniform dispersion of catalytically effective amounts of a platinum group component, which is maintained in the elemental metallic state during the incorporation of the rhenium carbonyl component, and of a bismuth component. In a highly preferred embodiment, this novel catalytic composite also contains a catalytically effective amount of a halogen component. The platinum group component, pyrolyzed rhenium carbonyl component, bismuth component and optional halogen component are preferably present in the multimetallic catalytic composite in amounts, calculated on an elemental basis, corresponding to about 0.01 to about 2 wt. % platinum group metal, about 0.01 to about 5 wt. % rhenium, about 0.01 to about 5 wt. % bismuth about 0.1 to about 3.5 wt. % halogen. A key feature associated with the preparation of the subject catalytic composite is reaction of a rhenium carbonyl complex with a porous carrier material containing a uniform dispersion of a bismuth component and of a platinum group metal maintained in the elemental state, whereby the interaction of the rhenium moiety with the platinum group moiety is maximized due to the platinophilic (i.e. platinum-seeking) propensities of the carbon monoxide ligands associated with the rhenium reagent.

CROSS-REFERENCE TO RELATED DISCLOSURES

This application is a division of my prior, copending application Ser.No. 970,049 filed Dec. 15, 1978, and issued as U.S. Pat. No. 4,235,705on Nov. 25, 1980 which in turn is a continuation-in-part of my priorapplication Ser. No. 833,332 filed Sept. 14, 1977 and issued Aug. 21,1979 as U.S. Pat. No. 4,165,276. All of the teachings of this priorapplication are specifically incorporated herein by reference.

The subject of the present invention is a novel attenuated superactivemultimetallic catalytic composite which has remarkably superioractivity, selectivity and resistance to deactivation when employed in ahydrocarbon conversion process that requires a catalytic agent havingboth a hydrogenation-dehydrogenation function and a carboniumion-forming function. The present invention, more precisely, involves anovel dual-function attenuated superactive multimetallic catalyticcomposite which quite surprisingly enables substantial improvements inhydrocarbon conversion processes that have traditionally used a platinumgroup metal-containing, dual-function catalyst. According to anotheraspect, the present invention comprehends the improved processes thatare produced by the use of the instant attenuated superactiveplatinum-rhenium-bismuth catalyst system which is characterized by aunique reaction between a rhenium carbonyl complex and a porous carriermaterial containing a uniform dispersion of a bismuth conponent and of aplatinum group component maintained in the elemental metallic state,whereby the interaction between the rhenium moiety and the platinumgroup moiety is maximized on an atomic level. In a specific aspect, thepresent invention concerns a catalytic reforming process which utilizesthe subject catalyst to markedly improve activity, selectivity andstability characteristics associated therewith to a degree notheretofore realized for platinum-rhenium, platinum-bismuth orplatinum-rhenium-bismuth catalyst systems. Specific advantagesassociated with use of the present attenuated superactiveplatinum-rhenium-bismuth catalyst system in a catalytic reformingprocess relative to those observed with the conventionalplatinum-rhenium, platinum-bismuth or platinum-rhenium-bismuth catalystsystems are: (1) increased ability to make octane at low severityoperating conditions; (2) substantially enhanced capability to maximizeC₅ + reformate and hydrogen production; (3) augmented ability to expandcatalyst life before regeneration becomes necessary in conventionaltemperature-limited catalytic reforming units; (4) increased toleranceto conditions which are known to increase the rate of production ofdeactivating coke deposits; (5) diminished requirements for amount ofcatalyst to achieve same results as the prior art catalyst systems at nosacrifice in catalyst life before regeneration; and (6) capability ofoperating at increased charge rates with the same amount of catalyst andat similar conditions as the prior art catalyst systems without anysacrifice in catalyst life before regeneration.

Composites having a hydrogenation-dehydrogenation function and acarbonium ion-forming function are widely used today as catalysts inmany industries, such as the petroleum and petrochemical industry, toaccelerate a wide spectrum of hydrocarbon conversion reactions.Generally, the carbonium ion-forming function is thought to beassociated with an acid-acting material of the porous, adsorptive,refractory oxide type which is typically utilized as the support orcarrier for a heavy metal component such as the metals or compounds ofmetals of Groups V through VIII of the Periodic Table to which aregenerally attributed the hydrogenation-dehydrogenation function.

These catalytic composites are used to accelerate a wide variety ofhydrocarbon conversion reactions such as hydrocracking, hydrogenolysis,isomerization, dehydrogenation, hydrogenation, desulfurization,cyclization, polymerization, alkylation, cracking, hydroisomerization,dealkylation, transalkylation, etc. In many cases, the commercialapplications of these catalysts are in processes where more than one ofthe reactions are proceeding simultaneously. An example of this type ofprocess is reforming wherein a hydrocarbon feedstream containingparaffins and naphthenes is subjected to conditions which promotedehydrogenation of naphthenes to aromatics, dehydrocyclization ofparaffins to aromatics, isomerization of paraffins and naphthenes,hydrocracking and hydrogenolysis of naphthenes and paraffins, and thelike reactions, to produce an octane-rich or aromatic-rich productstream. Another example is a hydrocracking process wherein catalysts ofthis type are utilized to effect selective hydrogenation and cracking ofhigh molecular weight unsaturated materials, selective hydrocracking ofhigh molecular weight materials, and other like reactions, to produce agenerally lower boiling; more valuable output stream. Yet anotherexample is a hydroisomerization process wherein a hydrocarbon fractionwhich is relatively rich in straight-chain-paraffin compounds iscontacted with a dual-function catalyst to produce an output stream richin isoparaffin compounds.

Regardless of the reaction involved or the particular process involved,it is of critical importance that the dual-function catalyst exhibit notonly the capability to initially perform its specified functions, butalso that it has the capability to perform them satisfactorily forprolonged periods of time. The analytical terms used in the art tomeasure how well a particular catalyst performs its intended functionsin a particular hydrocarbon reaction environment are activity,selectivity, and stability. And for purposes of discussion here, theseterms are conveniently defined for a given charge stock as follows: (1)activity is a measure of the catalyst's ability to convert hydrocarbonreactants into products at a specified severity level where severitylevel means the conditions used--that is, the temperature, pressure,contact time, and presence of diluents such as H₂ ; (2) selectivityrefers to the amount of desired product or products obtained relative tothe amount of reactants charged or converted; (3) stability refers tothe rate of change with time of the activity and selectivityparameters--obviously, the smaller rate implying the more stablecatalyst. In a reforming process, for example, activity commonly refersto the amount of conversion that takes place for a given charge stock ata specified severity level and is typically measured by octane number ofthe C₅ + product stream; selectivity refers to the amount of C₅ + yield,relative to the amount of the charge, that is obtained at the particularactivity or severity level; and stability is typically equated to therate of change with time of activity, as measured by octane number ofC₅ + product and of selectivity as measured by C₅ + yield. Actually thelast statement is not strictly correct because generally a continuousreforming process is run to produce a constant octane C₅ + product withseverity level being continuously adjusted to attain this result; andfurthermore, the severity level is for this process usually varied byadjusting the conversion temperature in the reaction so that, in pointof fact, the rate of change of activity finds response in the rate ofchange of conversion temperatures and changes in this last parameter arecustomarily taken as indicative of activity stability.

As is well known to those skilled in the art, the principal cause ofobserved deactivation or instability of a dual-function catalyst when itis used in a hydrocarbon conversion reaction is associated with the factthat coke forms on the surface of the catalyst during the course of thereaction. More specifically, in these hydrocarbon conversion processesthe conditions utilized typically result in the formation of heavy, highmolecular weight, black, solid or semi-solid, carbonaceous materialwhich is a hydrogen-deficient polymeric substance having properties akinto both polynuclear aromatics and graphite. This material coats thesurface of the catalyst and thus reduces its activity by shielding itsactive sites from the reactants. In other words, the performance of thisdual-function catalyst is sensitive to the presence of carbonaceousdeposits or coke on the surface of the catalyst. Accordingly, the majorproblem facing workers in this area of the art is the development ofmore active and/or selective catalytic composites that are not assensitive to the presence of these carbonaceous materials and/or havethe capability to suppress the rate of the formation of thesecarbonaceous materials on the catalyst. Viewed in terms of performanceparameters, the problem is to develop a dual-function catalyst havingsuperior activity, selectivity, and stability characteristics. Inparticular, for a reforming process the problem is typically expressedin terms of shifting and stabilizing the C₅ + yield-octane relationshipat the lowest possible severity level--C₅ + yield being representativeof selectivity and octane being proportional to activity.

I have now found a dual-function attenuated superactive multimetalliccatalytic composite which possesses improved activity, selectivity andstability characteristics relative to similar catalysts of the prior artwhen it is employed in a process for the conversion of hydrocarbons ofthe type which have heretofore utilized dual-function, platinum groupmetal-containing catalytic composites such as processes forisomerization, hydroisomerization, dehydrogenation, desulfurization,denitrogenization, hydrogenation, alkylation, dealkylation,disproportionation, polymerization, hydroealkylation, transalkylation,cyclization, dehydrocyclization, cracking, hydrocracking, halogenation,reforming and the like processes. In particular, I have now establishedthat an attenuated superactive multimetallic catalytic composite,comprising a combination of a catalytically effective amount of apyrolyzed rhenium carbonyl component with a porous carrier materialcontaining catalytically effective amounts of a platinum group componentand a bismuth component, can enable the performance of hydrocarbonconversion processes utilizing dual-function catalysts to besubstantially improved if the platinum group component is relativelyuniformly dispersed throughout the porous carrier material prior tocontact with the rhenium carbonyl reagent, if the oxidation state of theplatinum group metal is maintained in the elemental metallic state priorto and during contact with the rhenium carbonyl reagent and if hightemperature treatment in the presence of oxygen and/or water of theresulting reaction product is avoided. A specific example of mydiscovery involves my finding that an attenuated superactive acidicmultimetallic catalytic composite, comprising a halogenated combinationof a catalytically effective amount of a pyrolyzed rhenium carbonylcomponent with a porous carrier material containing a uniform dispersionof catalytically effective amounts of a platinum group componentmaintained in the elemental metallic state and of a bismuth component,can be utilized to substantially improve the performance of ahydrocarbon reforming process which operates on a low octane gasolinefraction to produce a high octane reformate or aromatic-rich reformate.In the case of a reforming process, some of the major advantagesassociated with the use of the novel multimetallic catalytic compositeof the present invention include: (1) acquisition of the capability tooperate in a stable manner in a high severity operation; for example, alow or moderate pressure reforming process designed to produce a C₅ +reformate having an octane of at least about 100 F-1 clear; (2)increased average activity for octane-upgrading reactions relative tothe performance of (a) prior art bimetallic platinum-rhenium catalystsystems as exemplified by the teachings of Kluksdahl in his U.S. Pat.No. 3,415,737 and (b) prior art platinum-bismuth andplatinum-rhenium-bismuth catalyst systems as shown in the teachings ofU.S. Pat. Nos. 3,156,737; 3,511,888; 3,798,155 and 3,859,201; and (3)substantially increased capability to maximize C₅ + yield and hydrogenproduction relative to these prior art catalyst systems. In sum, thepresent invention involves the remarkable finding that the addition of apyrolyzed rhenium carbonyl component to a porous carrier materialcontaining a uniform dispersion of a catalytically effective amount of aplatinum group component maintained in the elemental metallic state andof a bismuth component, can enable the performance characteristics ofthe resulting attenuated superactive multimetallic catalytic compositeto be sharply and materially improved relative to those associated withthe prior art platinum-rhenium, platinum-bismuth andplatinum-rhenium-bismuth catalyst systems.

It is, accordingly, an object of the present invention to provide anattenuated superactive multimetallic hydrocarbon conversion catalysthaving superior performance characteristics relative to the prior artplatinum-rhenium, platinum-bismuth and platinum-rhenium-bismuth catalystsystems when utilized in a hydrocarbon conversion process. A secondobject is to provide an attenuated superactive multimetallic acidiccatalyst having dual-function hydrocarbon conversion performancecharacteristics which are relatively insensitive to the deposition ofcoke-forming, hydrocarbonaceous materials thereon and to the presence ofsulfur contaminants in the reaction environment. A third object is toprovide preferred methods of preparation of this attenuated superactivemultimetallic catalytic composite which methods insure the achievementand maintenance of its unique properties. Another object is to providean improved platinum-pyrolyzed-rhenium-carbonyl catalyst system havingsuperior selectivity characteristics relative to theplatinum-pyrolyzed-rhenium-carbonyl catalyst system disclosed in myprior application Ser. No. 833,332, now U.S. Pat. No. 4,165,276. Anotherobject is to provide a novel acidic multimetallic hydrocarbon conversioncatalyst which utilizes a pyrolyzed rhenium carbonyl component tobeneficially interact with and selectively promote an acidic catalystcontaining a bismuth component, a halogen component and a uniformdispersion of a platinum group component maintained in the metallicstate during the incorporation of the rhenium carbonyl component.

The three Figures of the drawing are graphical representations of theresults obtained in the examples.

Without the intention of being limited by the following explanation, Ibelieve my discovery that rhenium carbonyl can, quite unexpectedly, beused under the circumstances described herein to synthesize an entirelynew type of platinum-rhenium-bismuth catalyst system, is attributable toone or more unusual and unique routes to greater platinum-rheniuminteraction that are opened or made available by the novel chemistryassociated with the reaction of a rhenium carbonyl reactant with asupported, uniformly dispersed platinum metal. Before considering indetail each of these possible routes to greater platinum-rheniuminteraction it is important to understand that: (1) "platinum" is usedherein to mean any one of the platinum group metals; (2) the unexpectedresults achieved with my catalyst systems are measured relative to theconventional platinum-rhenium, platinum-bismuth andplatinum-rhenium-bismuth catalyst systems and relative to the catalystsystem of my prior invention as disclosed in my prior application Ser.No. 833,332; (3) the expression "rhenium moiety" is intended to mean thecatalytically active form of the rhenium entity derived from the rheniumcarbonyl component in the present catalyst system; (4) metalliccarbonyls have been suggested generally in the prior art for use inmaking catalysts such as in U.S. Pat. Nos. 2,798,051, 3,591,649 and4,048,110, but no one to my knowledge has ever suggested using thesereagents in the platinum-rhenium or platinum-rhenium-bismuth catalystsystems, particularly where substantially all of the platinum componentof the catalyst is present in a reduced form (i.e. the metal) prior toand during the incorporation of the rhenium carbonyl component. Oneroute to greater platinum-rhenium interaction enabled by the presentinvention comes from the theory that the effect of rhenium on a platinumcatalyst is very sensitive to the particle size of the rhenium moiety;since in my procedure the rhenium is put on the catalyst in a form whereit is complexed with a carbon monoxide molecule which is known to have astrong affinity for platinum, it is reasonable to assume that when theplatinum is widely dispersed on the support, one effect of the CO ligandis to pull the rhenium moiety towards the platinum sites on thecatalyst, thereby achieving a dispersion and particle size of therhenium moiety in the catalyst which closely imitates the correspondingplatinum conditions (i.e. this might be called a piggy-back theory). Thesecond route to greater platinum-rhenium interaction is similar to thefirst and depends on the theory that the effect of rhenium on a platinumcatalyst is at a maximum when the rhenium moiety is attached toindividual platinum sites, the use of platinophilic CO ligands, ascalled for by the present invention, then acts to facilitate adsorptionor chemisorption of the rhenium moiety on the platinum site so that asubstantial portion of the rhenium moiety is deposited or fixed on ornear the platinum site where the platinum acts to anchor the rhenium,thereby making it more resistant to sintering at high temperature. Thethird route to greater platinum-rhenium interaction is based on thetheory that the active state for the rhenium moiety in therhenium-platinum catalyst system is the elemental metallic state andthat the best platinum-rhenium interaction is achieved when theproportion of the rhenium in the metallic state is maximized; using arhenium carbonyl compound to introduce the rhenium into the catalyticcomposite conveniently ensures availability of more rhenium metalbecause all of the rhenium in this reagent is present in the elementalmetallic state. Another route to greater platinum-rhenium interaction isderived from the theory that oxygen at high temperature is detrimentalto both the active form of the rhenium moiety (i.e. the metal) and thedispersion of same on the support (i.e. oxygen at high temperatures issuspected of causing sintering of the rhenium moiety); since thecatalyst of the present invention is not subject to high temperaturetreatment with oxygen after rhenium is incorporated, maximumplatinum-rhenium interaction is obviously preserved. The final theoryfor explaining the greater platinum-rhenium interaction associated withthe instant catalyst is derived from the idea that the active sites forthe platinum-rhenium catalyst are basically platinum metal crystallitesthat have had their surface enriched in rhenium metal; since the conceptof the present invention requires the rhenium to be laid down on thesurface of well-dispersed platinum crystallites via a platinophilicrhenium carbonyl complex, the probability of surface enrichment isgreatly increased for the present procedure relative to that associatedwith the random, independent dispersion of both crystallites that hascharacterized the prior art preparation procedures. It is of course tobe recognized that all of these factors may be involved to some degreein the overall explanation of the impressive results associated with myattenuated superactive catalyst system. A further fact to be kept inmind is that the conventional platinum-rhenium catalyst system has neverbeen noted for an activity improvement (i.e. the consensus of the art isthat they give the same activity as the all platinum catalyst system)but its strong suit has always been very impressive stability; incontrast, my attenuated superactive platinum-rhenium-bismuth catalystsystem in a hydrocarbon reforming process, for example, gives betteraverage activity than the conventional platinum-rhenium catalyst systemand, even more surprising, this activity advantage is achieved withoutsacrificing hydrogen and C₅ + selectivity.

Against this background then, the present invention is in oneembodiment, a novel trimetallic catalytic composite comprising acombination of a catalytically effective amount of a pyrolyzed rheniumcarbonyl component with a porous material containing a uniformdispersion of catalytically effective amounts of a platinum groupcomponent maintained in the elemental metallic state during theincorporation of the rhenium carbonyl component and of a bismuthcomponent.

In another embodiment, the subject catalytic composite comprises acombination of a catalytically effective amount of a pyrolyzed rheniumcarbonyl component with a porous carrier material containing acatalytically effective amount of a halogen component and a uniformdispersion of catalytically effective amounts of a platinum groupcomponent maintained in the elemental metallic state during theincorporation of the rhenium carbonyl component and of a bismuthcomponent.

In yet another embodiment the present invention involves a hydrocarbonconversion catalyst comprising a combination of a pyrolyzed rheniumcarbonyl component with a porous carrier material containing a halogencomponent and a uniform dispersion of a platinum group componentmaintained in the elemental metallic state during the incorporation ofthe rhenium carbonyl component and of a bismuth component, wherein thesecomponents are present in amounts sufficient to result in the compositecontaining, calculated on an elemental basis, about 0.01 to about 2 wt.% platinum group metal, about 0.01 to about 5 wt. % rhenium, about 0.01to about 5 wt. % bismuth, and about 0.1 to about 3.5 wt. % halogen.

In still another embodiment, the present invention comprises any of thecatalytic composites defined in the previous embodiments wherein theporous carrier material contains, prior to the addition of the pyrolyzedrhenium carbonyl component, not only a platinum group component and abismuth component but also a catalytically effective amount of acomponent selected from the group consisting of tin, lead, germanium,cobalt, zirconium, nickel, iron, zinc, tungsten, chromium, molybdenum,manganese, indium, gallium, cadmium, tantalum, uranium, copper, silver,gold, one or more of the rare earth metals and mixtures thereof.

In another aspect, the invention is defined as a catalytic compositecomprising the pyrolyzed reaction product formed by reacting acatalytically effective amount of a rhenium carbonyl complex with aporous carrier material containing a uniform dispersion of catalyticallyeffective amounts of a platinum group component maintained in theelemental metallic state and of a bismuth component, and thereaftersubjecting the resulting reaction product to pyrolysis conditionsselected to decompose the resulting rhenium carbonyl component.

A concomitant embodiment of the present invention involves a method ofpreparing any of the catalytic composites defined in the previousembodiments, the method comprising the steps of: (a) reacting a rheniumcarbonyl complex with a porous carrier material containing a uniformdispersion of a platinum group component maintained in the elementalmetallic state and of a bismuth component, and thereafter, (b)subjecting the resulting reaction product to pyrolysis conditionsselected to decompose the resulting rhenium carbonyl component, withoutoxidizing either the platinum group or rhenium components.

A further embodiment involves a process for the conversion of ahydrocarbon which comprises contacting the hydrocarbon and hydrogen withthe attenuated superactive catalytic composite defined in any of theprevious embodiments at hydrocarbon conversion conditions.

A highly preferred embodiment comprehends a process for reforming agasoline fraction which comprises contacting the gasoline fraction andhydrogen with the attenuated superactive multimetallic catalyticcomposites defined in any one of the prior embodiments at reformingconditions selected to produce a high octane reformate.

An especially preferred embodiment is a process for the production ofaromatic hydrocarbons which comprises contacting a hydrocarbon fractionrich in aromatic precursors and hydrogen with an acidic catalyticcomposite comprising a combination of a catalytically effective amountof a pyrolyzed rhenium carbonyl component with a porous carrier materialcontaining catalytically effective amounts of a halogen component and ofa bismuth component, and a uniform dispersion of a catalyticallyeffective amount of a platinum group component maintained in theelemental metallic state during the incorporation of the rheniumcarbonyl component. This contacting is performed at aromatic productionconditions selected to produce an effluent stream rich in aromatichydrocarbons.

Other objects and embodiments of the present invention relate toadditional details regarding the essential and preferred catalyticingredients, preferred amounts of ingredients, appropriate methods ofcatalyst preparation, operating conditions for use with the novelcatalyst in the various hydrocarbon conversion processes in which it hasutility, and the like particulars, which are hereinafter given in thefollowing detailed discussion of each of the essential and preferredfeatures of the present invention.

Considering first the porous carrier material utilized in the presentinvention, it is preferred that the material be a porous, adsorptive,high surface area support having a surface area of about 25 to about 500m² /g. The porous carrier material should be relatively refractory tothe conditions utilized in the hydrocarbon conversion process, and it isintended to include within the scope of the present invention carriermaterials which have traditionally been utilized in dual-functionhydrocarbon conversion catalysts such as: (1) activated carbon, coke, orcharcoal; (2) silica or silica gel, silicon carbide, clays, andsilicates including those synthetically prepared and naturallyoccurring, which may or may not be acid treated for example, attapulgusclay, china clay, diatomaceous earth, fuller's earth, kaolin,kieselguhr, etc., (3) ceramics, porcelain, crushed firebrick, bauxite;(4) refractory inorganic oxides such as alumina, titanium dioxide,zirconium dioxide, chromium oxide, beryllium oxide, vanadium oxide,cesium oxide, hafnium oxide, zinc oxide, magnesia, boria, thoria,silica-alumina, silica-magnesia, chromia-alumina, alumina-boria,silica-zirconia, etc.; (5) crystalline zeolitic alumino-silicates suchas naturally occurring or synthetically prepared mordenite and/orfaujasite, either in the hydrogen form or in a form which has beentreated with multivalent cations; (6) spinels such as MgAl₂ O₄, FeAl₂O₄, ZnAl₂ O₄, CaAl₂ O₄, and other like compounds having the formulaMO-Al₂ O₃ where M is a metal having a valence of 2; and (7) combinationsof elements from one or more of these groups. The preferred porouscarrier materials for use in the present invention are refractoryinorganic oxides, with best results obtained with an alumina carriermaterial. Suitable alumina materials are the crystalline aluminas knownas gamma-, eta-, and theta-alumina, with gamma- or eta-alumina givingbest results. In addition, in some embodiments the alumina carriermaterial may contain minor proportions of other well known refractoryinorganic oxides such as silica, zirconia, magnesia, etc.; however, thepreferred support is substantially pure gamma- or eta-alumina. Preferredcarrier materials have an apparent bulk density of about 0.3 to about0.8 g/cc and surface area characteristics such that the average porediameter is about 20 to 300 Angstroms, the pore volume (B.E.T.) is about0.1 to about 1 cc/g and the surface area (B.E.T.) is about 100 to about500 m² /g. In general, best results are typically obtained with agamma-alumina carrier material which is used in the form of sphericalparticles having: a relatively small diameter (i.e. typically about 1/16inch), an apparent bulk density of about 0.3 to about 0.8 g/cc, a porevolume (B.E.T.) of about 0.4 cc/g. and a surface area (B.E.T.) of about150 to about 250 m² /g.

The preferred alumina carrier material may be prepared in any suitablemanner and may be synthetically prepared or natural occurring. Whatevertype of alumina is employed, it may be activated prior to use by one ormore treatments including drying, calcination, steaming, etc., and itmay be in a form known as activated alumina, activated alumina ofcommerce, porous alumina, alumina gel, etc. For example, the aluminacarrier may be prepared by adding a suitable alkaline reagent, such asammonium hydroxide, to a salt of aluminum such as aluminum chloride,aluminum nitrate, etc., in an amount to form an aluminum hydroxide gelwhich upon drying and calcining is converted to alumina. The aluminacarrier may be formed in any desired shape such as spheres, pills,cakes, extrudates, powders, granules, tablets, etc., and utilized in anydesired size. For the purpose of the present invention a particularlypreferred form of alumina is the sphere, and alumina spheres may becontinuously manufactured by the well known oil drop method whichcomprises: forming an alumina hydrosol by any of the techniques taughtin the art and preferably by reacting aluminum metal with hydrochloricacid, combining the resultant hydrosol with a suitable gelling agent anddropping the resultant mixture into an oil bath maintained at elevatedtemperatures. The droplets of the mixture remain in the oil bath untilthey set and form hydrogel spheres. The spheres are then continuouslywithdrawn from the oil bath and typically subjected to specific agingtreatments in oil and an ammoniacal solution to further improve theirphysical characteristics. The resulting aged and gelled particles arethen washed and dried at a relatively low temperature of about 300° F.to about 400° F. and subjected to a calcination procedure at atemperature of about 850° F. to about 1300° F. for a period of about 1to about 20 hours. This treatment effects conversion of the aluminahydrogel to the corresponding crystalline gamma-alumina. See theteachings of U.S. Pat. No. 2,620,314 for additional details.

Another particularly preferred alumina carrier material is synthesizedfrom a unique crystalline alumina powder which has been characterized inU.S. Pat. Nos. 3,852,190 and 4,012,313 as a byproduct from a Zieglerhigher alcohol synthesis reaction as described in Ziegler's U.S. Pat.No. 2,892,858. For purposes of simplification, the name "Ziegleralumina" is used herein to identify this material. It is presentlyavailable from the Conoco Chemical Division of Continental Oil Companyunder the trademark Catapal. This material is an extremely high purityalpha-alumina monohydrate (boehmite) which after calcination at a hightemperature has been shown to yield a high purity gamma-alumina. It iscommercially available in three forms: (1) Catapal SB--a spray driedpowder having a typical surface area of 250 m² /g; (2) Catapal NG--arotary kiln dried alumina having a typical surface area of 180 m² /g;and (3) Dispel M--a finely divided dispersable product having a typicalsurface area of about 185 m² /g. For purposes of the present invention,the preferred starting material is the spray dried powder, Catapal SB.This alpha-alumina monohydrate powder may be formed into a suitablecatalyst material according to any of the techniques known to thoseskilled in the catalyst carrier material forming art. Spherical carriermaterial particles can be formed, for example, from this Ziegler aluminaby: (1) converting the alpha-alumina monohydrate powder into an aluminasol by reaction with a suitable peptizing agent and water and thereafterdropping a mixture of the resulting sol and a gelling agent into an oilbath to form spherical particles of an alumina gel which are easilyconverted to a gamma-alumina carrier material by known methods; (2)forming an extrudate from the powder by established methods andthereafter rolling the extrudate particles on a spinning disc untilspherical particles are formed which can then be dried and calcined toform the desired particles of spherical carrier material; and (3)wetting the powder with a suitable peptizing agent and thereafterrolling particles of the powder into spherical masses of the desiredsize in much the same way that children have been known to make parts ofsnowmen by rolling snowballs down hills covered with wet snow. Thisalumina powder can also be formed in any other desired shape or type ofcarrier material known to those skilled in the art such as rods, pills,pellets, tablets, granules, extrudates and the like forms by methodswell known to the practitioners of the catalyst carrier material formingart. The preferred type of carrier material for the present invention isa cylindrical extrudate having a diameter of about 1/32" to about 1/8"(especially about 1/16") and a length to diameter (L/D) ratio of about1:1 to about 5:1, with a L/D ratio of about 2:1 being especiallypreferred. The especially preferred extrudate form of the carriermaterial is preferably prepared by mixing the alumina powder with waterand a suitable peptizing agent such as nitric acid, acetic acid,aluminum nitrate and the like material until an extrudable dough isformed. The amount of water added to form the dough is typicallysufficient to give a loss on ignition (LOI) at 500° C. of about 45 to 65wt. %, with a value of about 55 wt. % being especially preferred. On theother hand, the acid addition rate is generally sufficient to provideabout 2 to 7 wt. % of the volatile free alumina powder used in the mix,with a value of about 3 to 4% being especially preferred. The resultingdough is then extruded through a suitable sized die to form extrudateparticles. These particles are then dried at a temperature of about 500°to 800° F. for a period of about 0.1 to about 5 hours and thereaftercalcined at a temperature of about 900° F. to about 1500° F. for aperiod of about 0.5 to about 5 hours to form the preferred extrudateparticles of the Ziegler alumina carrier material. In addition, in someembodiments of the present invention the Ziegler alumina carriermaterial may contain minor proportions of other well known refractoryinorganic oxides such as silica, titanium dioxide, zirconium dioxide,chromium oxide, beryllium oxide, vanadium oxide, cesium oxide, hafniumoxide, zinc oxide, iron oxide, cobalt oxide, magnesia, boria, thoria,and the like materials which can be blended into the extrudable doughprior to the extrusion of same. In the same manner crystalline zeoliticaluminosilicates such as naturally occurring or synthetically preparedmordenite and/or faujasite, either in the hydrogen form or in a formwhich has been treated with a multivalent cation, such as a rare earth,can be incorporated into this carrier material by blending finelydivided particles of same into the extrudable dough prior to extrusionof same. A preferred carrier material of this type is substantially pureZiegler alumina having an apparent bulk density (ABD) of about 0.6 to 1g/cc (especially an ABD of about 0.7 to about 0.85 g/cc), a surface area(B.E.T.) of about 150 to about 280 m² /g (preferably about 185 to about235 m² /g.) and a pore volume (B.E.T.) of about 0.3 to about 0.8 cc/g.

A first essential ingredient of the subject catalyst is the platinumgroup component. That is, it is intended to cover the use of platinum,iridium, osmium, ruthenium, rhodium, palladium, or mixtures thereof as afirst component of the attenuated superactive catalytic composite. It isan essential feature of the present invention that substantially all ofthis platinum group component is uniformly dispersed throughout theporous carrier material in the elemental metallic state prior to andduring the incorporation of the rhenium carbonyl ingredient. Generally,the amount of this component present in the form of catalytic compositesis small and typically will comprise about 0.01 to about 2 wt. % offinal catalytic composite, calculated on an elemental basis. Excellentresults are obtained when the catalyst contains about 0.05 to about 1wt. % of platinum, iridium, rhodium, palladium or ruthenium metal.Particularly preferred mixtures of these platinum group metals preferredfor use in the composite of the present invention are: (1) platinum andiridium, (2) platinum and rhodium, and (3) platinum and ruthenium.

This platinum group component may be incorporated into the porouscarrier material in any suitable manner known to result in a relativelyuniform distribution of this component in the carrier material such ascoprecipitation or cogelation, ion-exchange or impregnation. Thepreferred method of preparing the catalyst involves the utilization of asoluble, decomposable compound of platinum group metal to impregnate thecarrier material in a relatively uniform manner. For example, thiscomponent may be added to the support by commingling the latter with anaqueous solution of chloroplatinic or chloroiridic or chloropalladicacid. Other water-soluble compounds or complexes of platinum groupmetals may be employed in impregnation solutions and include ammoniumchloroplatinate, bromoplatinic acid, platinum trichloride, platinumtetrachloride hydrate, platinum dichlorocarbonyl dichloride,dinitrodiaminoplatinum, sodium tetranitroplatinate (II), palladiumchloride, palladium nitrate, palladium sulfate, diamminepalladium (II)hydroxide, tetramminepalladium (II) chloride, hexamminerhodium chloride,rhodium carbonylchloride, rhodium trichloride hydrate, rhodium nitrate,sodium hexachlororhodate (III), sodium hexanitrorhodate (III), iridiumtribromide, iridium dichloride, iridium tetrachloride, sodiumhexanitroiridate (III), potassium or sodium chloroiridate, potassiumrhodium oxalate, etc. The utilization of a platinum, iridium, rhodium,or palladium chloride compound, such as chloroplatinic, chloroiridic, orchloropalladic acid or rhodium trichloride hydrate, is preferred sinceit facilitates the incorporation of both the platinum group componentand at least a minor quantity of the preferred halogen component in asingle step. Hydrogen chloride or the like acid is also generally addedto the impregnation solution in order to further facilitate theincorporation of the halogen component and the uniform distribution ofthis metallic component throughout the carrier material. In addition, itis generally preferred to impregnate the carrier material after it hasbeen calcined in order to minimize the risk of washing away the valuableplatinum group compound.

A second essential constituent of the multimetallic catalyst of thepresent invention is a bismuth component. This component may in generalbe present in the instant catalytic composite in any catalyticallyactive form such as the elemental metal, a compound like the oxide,hydroxide, halide, oxyhalide, aluminate, or in chemical combination withone or more of the other ingredients of the catalyst. Although it is notintended to restrict the present invention by this explanation, it isbelieved that best results are obtained when the bismuth component ispresent in the composite in a form wherein substantially all of thebismuth moiety is in an oxidation state above that of the elementalmetal such as in the form of bismuth oxide or bismuth aluminate or amixture thereof and the subsequently described oxidation and reductionsteps that are preferably used in the preparation of the instantcatalytic composite are specifically designed to achieve this end. Theterm "bismuth aluminate" are used herein means a coordinated complex ofbismuth, oxygen, and aluminum which are not necessarily present in thesame fixed relationship for all cases covered herein. This bismuthcomponent can be used in any amount which is catalytically effective,with good results obtained, on an elemental basis, with about 0.01 toabout 5 wt. % bismuth in the catalyst. Best results are ordinarilyachieved with about 0.05 to about 1 wt. % bismuth, calculated on anelemental basis and with an atomic ratio of bismuth to platinum groupmetal of about 0.1:1 to about 5:1 and especially about 01:1 to about 1:1

This bismuth component may be incorporated into the porous carriermaterial in any suitable manner known to the art to result in arelatively uniform dispersion of the bismuth moiety in the carriermaterial, such as by coprecipitation or cogellation or coextrusion withthe porous carrier material, ion exchange with the gelled carriermaterial, or impregnation of the carrier material either after, before,or during the period when it is dried and calcined. It is to be notedthat it is intended to include within the scope of the present inventionall conventional methods for incorporating and simultaneously uniformlydistributing a metallic component in a catalytic composite and theparticular method of incorporation used is not deemed to be an essentialfeature of the present invention. One preferred method of incorporatingthe bismuth component into the catalytic composite involves cogelling orcoprecipitating or coextruding the bismuth component in the form of thecorresponding hydrous oxide during the preparation of the preferredcarrier material, alumina. This method typically involves the additionof a suitable sol-soluble or sol-dispersable bismuth compound such asbismuth trichloride, bismuth oxynitrate, and the like to the aluminahydrosol and then combining the hydrosol with a suitable gelling agentand dropping the resulting mixture into an oil bath, etc., as explainedin detail hereinbefore. Alternatively, the bismuth compound can be addedto the gelling agent. After drying and calcining the resultingbismuth-containing gelled carrier material in air, there is obtained anintimate combination of alumina and bismuth oxide and/or bismuthaluminate. Another method of incorporating the bismuth component intothe catalytic composite involves utilization of a soluble, decomposablecompound or complex of bismuth to impregnate the porous carriermaterial. In general, the solvent used in this impregnation step isselected on the basis of the capability to dissolve the desired bismuthcompound without adversely affecting the carrier material and may be asuitable alcohol, ether, acid, and the like solvent, although it ispreferably an aqueous, acidic solution. Thus, the bismuth component maybe added to the carrier material by commingling the latter with anaqueous acidic solution of suitable bismuth salt or complex of bismuthsuch as bismuth citrate, bismuth iodide, bismuth lactate, bismuthchloride, bismuth hydroxide, bismuth nitrate, bismuth oxynitrate,bismuth oxalate, bismuth sesquioxide, bismuth oxybromide, bismuthoxychloride, bismuthic acid, bismuth oxycarbonate, bismuth acetate,bismuth benzoate, bismuth bromide, bismuth tartrate, bismuth potassiumtartrate, bismuth sodium tartrate, bismuth ammonium citrate, and thelike compounds. A particularly preferred impregnation solution comprisesan acidic solution of bismuth trichloride or bismuth oxynitrate inwater. Suitable acids for use in the impregnation solution are:inorganic acids such as hydrochloric acid, nitric acid, and the like,and strongly acidic organic acids such as oxalic acid, malonic acid,citric acid, and the like. In general, the bismuth component can beimpregnated either prior to, simultaneously with, or after the platinumgroup component is added to the carrier material. However, especiallygood results are obtained when the bismuth component is added to thecarrier material before the platinum group component.

It is especially preferred to incorporate a halogen component into theplatinum group metal- and bismuth-containing porous carrier materialprior to the reactions thereof with the rhenium carbonyl reagent.Although the precise form of the chemistry of the association of thehalogen component with the catalytic composite is not entirely known, itis customary in the art to refer to the halogen component as beingcombined with the carrier material or with the platinum group and/orbismuth components in the form of the halide (e.g. as the chloride).This combined halogen may be either fluorine, chlorine, iodine, bromide,or mixtures thereof. Of these, fluorine and, particularly, chlorine arepreferred for the purposes of the present invention. The halogen may beadded to the carrier material in any suitable manner, either duringpreparation of the support or before or during or after the addition ofthe platinum group and bismuth components. For example, the halogen maybe added, at any stage of the preparation of the carrier material or tothe calcined carrier material, as an aqueous solution of a suitable,decomposable halogen-containing compound such as hydrogen fluoride,hydrogen chloride, hydrogen bromide, ammonium chloride, etc. The halogencomponent or a portion thereof, may be combined with the carriermaterial during the impregnation of the latter with the platinum groupand/or bismuth components, for example, through the utilization of amixture of chloroplatinic acid and hydrogen chloride. In anothersituation, the alumina hydrosol which is typically utilized to form apreferred alumina carrier material may contain halogen and thuscontribute at least a portion of the halogen component to the finalcomposite. For reforming, the halogen will be typically combined withthe carrier material in an amount sufficient to result in a finalcomposite that contains about 0.1 to about 3.5%, and preferably about0.5 to about 1.5%, by weight of halogen, calculated on an elementalbasis. In isomerization or hydrocracking embodiments, it is generallypreferred to utilize relatively larger amounts of halogen in thecatalyst--typically, ranging up to about 10 wt. % halogen calculated onan elemental basis, and more preferably, about 1 to about 5 wt. %. It isto be understood that the specified level of halogen component in theinstant attenuated superactive catalyst can be achieved or maintainedduring use in the conversion of hydrocarbons by continuously orperiodically adding to the reaction zone a decomposablehalogen-containing compound such as an organic chloride (e.g. ethylenedichloride, carbon tetrachloride, t-butyl chloride) in an amount ofabout 1 to 100 wt. ppm. of the hydrocarbon feed, and preferably about 1to 10 wt. ppm.

After the platinum group and bismuth components are combined with theporous carrier material, the resulting platinum group metal- andbismuth-containing carrier material will generally be dried at atemperature of about 200° F. to about 600° F. for a period of typicallyabout 1 to about 24 hours or more and thereafter oxidized at atemperature of about 700° F. to about 1100° F. in an air or oxygenatmosphere for a period of about 0.5 to about 10 or more hourssufficient to convert substantially all of the platinum group componentto the corresponding metallic oxide. When the preferred halogencomponent is utilized in the present composition, best results aregenerally obtained when the halogen content of the platinum group metal-and bismuth-containing carrier material is adjusted during at least aportion of this oxidation step by including a halogen orhalogen-containing compound in the air or oxygen atmosphere utilized.For purposes of the present invention, the particularly preferredhalogen is chlorine and it is highly recommended that the halogencompound utilized in this halogenation step be either hydrochloric acidor a hydrochloric acid-producing substance. In particular, when thehalogen component of the catalyst is chlorine, it is preferred to use amolar ratio of H₂ O to HCl of about 5:1 to about 100:1 during at least aportion of this oxidation step in order to adjust the final chlorinecontent of the catalyst to a range of about 0.1 to about 3.5 wt. %.Preferably, the duration of this halogenation step is about 1 to 5 ormore hours.

A crucial feature of the present invention involves subjecting theresulting oxidized, platinum group metal- and bismuth-containing, andtypically halogen-treated, carrier material to a substantiallywater-free reduction step before the incorporation of the rheniumcomponent by means of the rhenium carbonyl reagent. The importance ofthis reduction step comes from my observation that when an attempt ismade to prepare the instant catalytic composite without first reducingthe platinum group component, no significant improvement in theplatinum-rhenium-bismuth catalyst system is obtained. Put another way,it is my finding that it is essential for the platinum group componentto be well dispersed in the porous carrier material in the elementalmetallic state prior to incorporation of the rhenium component by theunique procedure of the present invention in order for synergisticinteraction of the rhenium carbonyl with the dispersed platinum groupmetal to occur according to the theories that I have previouslyexplained. Accordingly, this reduction step is designed to reducesubstantially all of the platinum group component to the elementalmetallic state and to assure a relatively uniform and finely divideddispersion of this metallic component throughout the porous carriermaterial. Preferably a substantially pure and dry hydrogen stream (bythe use of the word "dry" I mean that it contains less than 20 vol. ppm.water and preferably less than 5 vol. ppm. water) is used as thereducing agent in this step. The reducing agent is contacted with theoxidized, platinum group metal-and bismuth-containing carrier materialat conditions including a reduction temperature of about 450° F. toabout 1200° F., a gas hourly space velocity (GHSV) sufficient to rapidlydissipate any local concentrations of water formed during the reductionof the platinum group metal oxide, and a period of about 0.5 to about 10or more hours selected to reduce substantially all of the platinum groupcomponent to the elemental metallic state. Once this condition of finelydivided dispersed platinum group metal in the porous carrier material isachieved, it is important that environments and/or conditions that coulddisturb or change this condition be avoided; specifically, I much preferto maintain the freshly reduced carrier material containing the platinumgroup metal under a blanket of inert gas to avoid any possibility ofcontamination of same either by water or by oxygen.

A third essential ingredient of the present attenuated superactivecatalytic composite is a rhenium component which I have chosen tocharacterize as a pyrolyzed rhenium carbonyl component in order toemphasize that the rhenium moiety of interest in my invention is therhenium produced by decomposing a rhenium carbonyl in the presence of afinely divided dispersion of a platinum group metal and in the absenceof materials such as oxygen or water which could interfere with thebasic desired interaction of the rhenium carbonyl component with theplatinum group metal component as previously explained. In a view of thefact that all of the rhenium contained in a rhenium carbonyl complex ispresent in the elemental metallic state, an essential requirement forfull realization of the activity improvement associated with myinvention is that the resulting reaction product of the rhenium carbonylcompound or complex with the platinum group metal- and bismuth-loadedcarrier material is not subjected to conditions which could in any wayinterfere with the maintenance of the rhenium moiety in the elementalmetallic state; consequently, avoidance of any conditions which wouldtend to cause the oxidation of any portion of the rhenium ingredient orof the platinum group ingredient is a requirement for full realizationof the synergistic interaction enabled by the present invention. Thisrhenium component may be utilized in the resulting composite in anyamount that is catalytically effective with the preferred amounttypically corresponding to about 0.01 to about 5 wt. % thereof,calculated on an elemental rhenium basis. Best results are ordinarilyobtained with about 0.05 to about 1 wt. % rhenium. The traditional rulefor rhenium-platinum catalyst system is that best results are achievedwhen the amount of the rhenium component is set as a function of theamount of the platinum group component also hold for my composition;specifically, I find that best results with a rhenium to platinum groupmetal atomic ratio of about 0.1:1 to about 10:1 with an especiallyuseful range comprising about 0.2:1 to about 5:1 and with superiorresults achieved at an atomic ratio of rhenium to platinum group metalof about 1:1 to about 3:1.

The rhenium carbonyl ingredient may be reacted with the reduced platinumgroup metal-and bismuth-containing porous carrier material in anysuitable manner known to those skilled in the catalyst formulation artwhich results in relatively good contact between the rhenium carbonylcomplex and the platinum group component contained in the porous carriermaterial. One acceptable procedure for incorporating the rheniumcarbonyl compound into the composite involves sublimating the rheniumcarbonyl complex under conditions which enable it to pass into the vaporphase without being decomposed and thereafter contacting the resultingrhenium carbonyl sublimate with the platinum group metal-andbismuth-containing porous carrier material under conditions designed toachieve intimate contact of the rhenium carbonyl reagent with theplatinum group metal dispersed on the carrier material. Typically thisprocedure is performed under vacuum at a temperature of about 70° F. toabout 250° F. for a period of time sufficient to react the desiredamount of rhenium with the carrier material. In some cases, an inertcarrier gas such as nitrogen can be admixed with the rhenium carbonylsublimate in order to facilitate the intimate contacting of same withthe platinum-and bismuth-loaded porous carrier material. A particularlypreferred way of accomplishing this rhenium carbonyl reaction step is animpregnation procedure wherein the platinum- and bismuth-loaded porouscarrier material is impregnated with a suitable solution containing thedesired quantity of the rhenium carbonyl complex. For purposes of thepresent invention, organic solutions are preferred, although anysuitable solution may be utilized as long as it does not interact withthe rhenium carbonyl and cause decomposition of same. Obviously theorganic solution should be anhydrous in order to avoid detrimentalinteraction of water with the rhenium carbonyl complex. Suitablesolvents are any of the commonly available organic solvents such as oneof the available ethers, alcohols, ketones, aldehydes, paraffins,naphthenes and aromatic hydrocarbons, for example, acetone, acetylacetone, benzaldehyde, pentane, hexane, carbon tetrachloride, methylisopropyl ketone, benzene, n-butylether, diethyl ether, ethylene glycol,methyl isobutyl ketone, diisobutyl ketone and the like organic solvents.Best results are ordinarily obtained when the solvent is acetone;consequently, the preferred impregnation solution is rhenium carbonyldissolved in anhydrous acetone. The rhenium carbonyl complex suitablefor use in the present invention may be either the pure rhenium carbonylitself or a substituted rhenium carbonyl such as the rhenium carbonylhalides including the chlorides, bromides, and iodides and the likesubstituted rhenium carbonyl complexes. After impregnation of thecarrier material with the rhenium carbonyl component, it is importantthat the solvent be removed or evaporated from the catalyst prior todecomposition of the rhenium carbonyl component by means of thehereinafter described pyrolysis step. The reason for removal of thesolvent is that I believe that the presence of organic materials such ashydrocarbons or derivatives of hydrocarbons during the rhenium carbonylpyrolysis step is highly detrimental to the synergistic interactionassociated with the present invention. This solvent is removed bysubjecting the rhenium carbonyl impregnated carrier material to atemperature of about 100° F. to about 250° F. in the presence of aninert gas or under a vacuum condition until substantially no furthersolvent is observed to come off the impregnated material. In thepreferred case where acetone is used as the impregnation solvent, thisdrying of the impregnated carrier material typically takes about onehalf hour at a temperature of about 225° F. under moderate vacuumconditions.

After the rhenium carbonyl component is incorporated into the platinum-and bismuth-loaded porous carrier material, the resulting composite is,pursuant to the present invention, subjected to pyrolysis conditionsdesigned to decompose substantially all of the rhenium carbonylmaterial, without oxidizing either the platinum group or the decomposedrhenium carbonyl component. This step is preferably conducted in anatmosphere which is substantially inert to the rhenium carbonyl such asin a nitrogen or noble gas-containing atmosphere. Preferably thispyrolysis step takes place in the presence of a substantially pure anddry hydrogen stream. It is of course within the scope of the presentinvention to conduct the pyrolysis step under vacuum conditions. It ismuch preferred to conduct this step in the substantial absence of freeoxygen and substances that could yield free oxygen under the conditionsselected. Likewise it is clear that best results are obtained when thisstep is performed in the total absence of water and of hydrocarbons andother organic materials. I have obtained best results in pyrolyzingrhenium carbonyl while using an anhydrous hydrogen stream at pyrolysisconditions including a temperature of about 300° F. to about 900° F. ormore, preferably about 400° F. to about 750° F., a gas hourly spacevelocity of about 250 to about 1500 hr.⁻¹ for a period of about 0.5 toabout 5 or more hours until no further evolution of carbon monoxide isnoted. After the rhenium carbonyl component has been pyrolyzed, it is amuch preferred practice to maintain the resulting catalytic composite inan inert environment (i.e. a nitrogen or the like inert gas blanket)until the catalyst is loaded into a reaction zone for use in theconversion of hydrocarbons.

The resulting pyrolyzed catalytic composite may, in some cases, bebeneficially subjected to a presulfiding step designed to incorporate inthe catalytic composite from about 0.01 to about 1 wt. % sulfurcalculated on an elemental basis. Preferably, this presulfidingtreatment takes place in the presence of hydrogen and a suitabledecomposable sulfur-containing compound such as hydrogen sulfide, lowermolecular weight mercaptans, organic sulfides, etc. Typically, thisprocedure comprises treating the pyrolyzed catalyst with a sulfiding gassuch as a mixture of hydrogen and hydrogen sulfide containing about 10moles of hydrogen per mole of hydrogen sulfide at conditions sufficientto effect the desired incorporation of sulfur, generally including atemperature ranging from about 50° F. up to about 1000° F. It isgenerally a preferred practice to perform this presulfiding step undersubstantially water-free and oxygen-free conditions. It is within thescope of the present invention to maintain or achieve the sulfided stateof the present catalyst during use in the conversion of hydrocarbons bycontinuously or periodically adding a decomposable sulfur-containingcompound, selected from the above-mentioned hereinbefore, to the reactorcontaining the attenuated superactive catalyst in an amount sufficientto provide about 1 to 500 wt. ppm., preferably about 1 to about 20 wt.ppm. of sulfur, based on hydrocarbon charge. According to another modeof operation, this sulfiding step may be accomplished during thepyrolysis step by utilizing a rhenium carbonyl reagent which has asulfur-containing ligand or by adding H₂ S to the hydrogen stream whichis preferably used therein.

In embodiments of the present invention wherein the instant attenuatedsuperactive multimetallic catalytic composite is used for thedehydrogenation of dehydrogenatable hydrocarbons or for thehydrogenation of hydrogenatable hydrocarbons, it is ordinarily apreferred practice to include an alkali or alkaline earth metalcomponent in the composite before addition of the rhenium carbonylcomponent and to minimize or eliminate the preferred halogen component.More precisely, this optional ingredient is selected from the groupconsisting of the compounds of the alkali metals--cesium, rubidium,potassium, sodium, and lithium--and the compounds of the alkaline earthmetals--calcium, strontium, barium, and magnesium. Generally, goodresults are obtained in these embodiments when this componentconstitutes about 0.1 to about 5 wt. % of the composite, calculated onan elemental basis. This optional alkali or alkaline earth metalcomponent can be incorporated into the composite in any of the knownways, with impregnation with an aqueous solution of a suitablewater-soluble, decomposable compound being preferred.

Another optional ingredient for the attenuated superactive multimetalliccatalyst of the present invention is a Friedel-Crafts metal halidecomponent. This ingredient is particularly useful in hydrocarbonconversion embodiments of the present invention wherein it is preferredthat the catalyst utilized has a strong acid or cracking functionassociated therewith--for example, an embodiment wherein thehydrocarbons are to be hydrocracked or isomerized with the catalyst ofthe present invention. Suitable metal halides of the Friedel-Crafts typeinclude aliminum chloride, aluminum bromide, ferric chloride, ferricbromide, zinc chloride, and the like compounds, with the aluminumhalides and particularly aluminum chloride ordinarily yielding bestresults. Generally, this optional ingredient can be incorporated intothe composite of the present invention by any of the conventionalmethods for adding metallic halides of this type and either prior to orafter the rhenium carbonyl reagent is added thereto; however, bestresults are ordinarily obtained when the metallic halide is sublimedonto the surface of the carrier material after the rhenium is addedthereto according to the preferred method disclosed in U.S. Pat. No.2,999,074. The component can generally be utilized in any amount whichis catalytically effective, with a value selected from the range ofabout 1 to about 100 wt. % of the carrier material generally beingpreferred.

According to the present invention, a hydrocarbon charge stock andhydrogen are contacted with the instant attenuated superactivemultimetallic catalyst in a hydrocarbon conversion zone. This contactingmay be accomplished by using the catalyst in a fixed bed system, amoving bed system, a fluidized bed system, or in a batch type operation;however, in view of the danger of attrition losses of the valuablecatalyst and of well known operational advantages, it is preferred touse either a fixed bed system or a dense-phase moving bed system such asis shown in U.S. Pat. No. 3,725,249. It is also contemplated that thecontacting step can be performed in the presence of a physical mixtureof particles of the catalyst of the present invention and particles of aconventional dual-function catalyst of the prior art. In a fixed bedsystem, a hydrogen-rich gas and the charge stock are preheated by anysuitable heating means to the desired reaction temperature and then arepassed into a conversion zone containing a fixed bed of the attenuatedsuperactive multimetallic catalyst. It is, of course, understood thatthe conversion zone may be one or more separate reactors with suitablemeans therebetween to ensure that the desired conversion temperature ismaintained at the entrance to each reactor. It is also important to notethat the reactants may be contacted with the catalyst bed in eitherupward, downward, or radial flow fashion with the latter beingpreferred. In addition, the reactants may be in the liquid phase, amixed liquid-vapor phase, or a vapor phase when they contact thecatalyst, with best results obtained in the vapor phase.

In the case where the attentuated superactive multimetallic catalyst ofthe present invention is used in a reforming operation, the reformingsystem will typically comprise a reforming zone containing one or morefixed beds or dense-phase moving beds of the catalysts. In a multiplebed system, it is, of course, within the scope of the present inventionto use the present catalyst in less than all of the beds with aconventional dual-function catalyst being used in the remainder of thebeds. This reforming zone may be one or more separate reactors withsuitable heating means therebetween to compensate for the endothermicnature of the reactions that take place in each catalyst bed. Thehydrocarbon feed stream that is charged to this reforming system willcomprise hydrocarbon fractions containing naphthenes and paraffins thatboil within the gasoline range. The preferred charge stocks are thoseconsisting essentially of naphthenes and paraffins, although in somecases aromatics and/or olefins may also be present. This preferred classincludes straight run gasolines, natural gasolines, synthetic gasolines,partially reformed gasolines, and the like. On the other hand, it isfrequently advantageous to charge thermally or catalytically crackedgasolines or higher boiling fractions thereof. Mixtures of straight runand cracked gasolines can also be used to advantage. The gasoline chargestock may be a full boiling gasoline having an initial boiling point offrom about 50° F. to about 150° F. and an end boiling point within therange of from about 325° F. to about 425° F., or may be a selectedfraction thereof which generally will be a higher boiling fractioncommonly referred to as a heavy naphtha--for example, a naphtha boilingin the range of C₇ to 400° F. In some cases, it is also advantageous tocharge pure hydrocarbons or mixtures of hydrocarbons that have beenextracted from hydrocarbon distillates--for example, straight-chainparaffins--which are to be converted to aromatics. It is preferred thatthese charge stocks be treated by conventional catalytic pretreatmentmethods such as hydrorefining, hydrotreating, hydrodesulfurization,etc., to remove substantially all sulfurous, nitrogenous, andwater-yielding contaminants therefrom and to saturate any olefins thatmay be contained therein.

In other hydrocarbon conversion embodiments, the charge stock will be ofthe conventional type customarily used for the particular kind ofhydrocarbon conversion being effected. For example, in a typicalisomerization embodiment, the charge stock can be a paraffinic stockrich in C₄ to C₈ normal paraffins, or a normal butane-rich stock, or ann-hexane-rich stock, or a mixture of xylene isomers, or anolefin-containing stock, etc. In a dehydrogenation embodiment, thecharge stock can be any of the known dehydrogenatable hydrocarbons suchas an aliphatic compound containing 2 to 30 carbon atoms per molecule, aC₄ to C₃₀ normal paraffin, a C₈ to C₁₂ alkylaromatic, a naphthene, andthe like. In hydrocracking embodiments, the charge stock will betypically a gas oil, heavy cracked cycle oil, etc. In addition,alkylaromatics, olefins, and naphthenes can be conveniently isomerizedby using the catalyst of the present invention. Likewise, purehydrocarbons or substantially pure hydrocarbons can be converted to morevaluable products by using the acidic multimetallic catalyst of thepresent invention in any of the hydrocarbon conversion processes, knownto the art, that use a dual-function catalyst.

In a reforming embodiment, it is generally preferred to utilize theinstant superactive multimetallic catalytic composite in a substantiallywater-free environment. Essential to the achievement of this conditionin the reforming zone is the control of the water level present in thecharge stock and the hydrogen stream which is being charged to the zone.Best results are ordinarily obtained when the total amount of waterentering the conversion zone from any source is held to a level lessthan 50 ppm. and preferably less than 20 ppm. expressed as weight ofequivalent water in the charge stock. In general, this can beaccomplished by careful control of the water present in the charge stockand in the hydrogen stream. The charge stock can be dried by using anysuitable drying means known to the art, such as a conventional solidadsorbent having a high selectivity for water, for instance, sodium orcalcium crystalline aluminosilicates, silica gel, activated alumina,molecular sieves, anhydrous calcium sulfate, high surface area sodium,and the like adsorbents. Similarly, the water content of the chargestock may be adjusted by suitable stripping operations in afractionation column or like device. And in some cases, a combination ofadsorbent drying and distillation drying may be used advantageously toeffect almost complete removal of water from the charge stock. In anespecially preferred mode of operation, the charge stock is dried to alevel corresponding to less than 5 wt. ppm. of water equivalent. Ingeneral, it is preferred to maintain the hydrogen stream entering thehydrocarbon conversion zone at a level of about 10 vol. ppm. of water orless and most preferably about 5 vol. ppm. or less. If the water levelin the hydrogen stream is too high, drying of same can be convenientlyaccomplished by contacting the hydrogen stream with a suitable desiccantsuch as those mentioned above.

In the reforming embodiment, an effluent stream is withdrawn from thereforming zone and passed through a cooling means to a separation zone,typically maintained at about 25° F. to 150° F., wherein a hydrogen-richgas stream is separated from a high octane liquid product stream,commonly called an unstabilized reformate. When the water level in thehydrogen stream is outside the range previously specified, at least aportion of this hydrogen-rich gas stream is withdrawn from theseparating zone and passed through an adsorption zone containing anadsorbent selective for water. The resultant substantially water-freehydrogen stream can then be recycled through suitable compressing meansback to the reforming zone. The liquid phase from the separating zone istypically withdrawn and commonly treated in a fractionating system inorder to adjust the butane concentration, thereby controlling front-endvolatility of the resulting reformate.

The operating conditions utilized in the numerous hydrocarbon conversionembodiments of the present invention are in general those customarilyused in the art for the particular reaction, or combination ofreactions, that is to be effected. For instance, alkylaromatic, olefin,and paraffin isomerization conditions include: a temperature of about32° F. to about 1000° F. and preferably from about 75° F. to about 600°F., a pressure of atmospheric to about 100 atmospheres, a hydrogen tohydrocarbon mole ratio of about 0.5:1 to about 20:1, and an LHSV(calculated on the basis of equivalent liquid volume of the charge stockcontacted with the catalyst per hour divided by the volume of conversionzone containing catalyst and expressed in units of hr.⁻¹) of about 0.2to 10. Dehydrogenation conditions include: a temperature of about 700°F. to about 1250° F., a pressure of about 0.1 to about 10 atmospheres, aliquid hourly space velocity of about 1 to 40, and a hydrogen tohydrocarbon mole ratio of about 1:1 to 20:1. Likewise, typicalhydrocracking conditions include: a pressure of about 500 psig. to about3000 psig., a temperature of about 400° F. to about 900° F., an LHSV ofabout 0.1 to about 10, and hydrogen circulation rates of about 1000 to10,000 SCF per barrel of charge.

In the reforming embodiment of the present invention, the pressureutilized is selected from the range of about 0 psig. to about 1000psig., with the preferred pressured being about 50 psig. to about 600psig. Particularly good results are obtained at low or moderatepressure; namely, a pressure of about 100 to 450 psig. In fact, it is asingular advantage of the present invention that it allows stableoperation at lower pressure than have heretofore been successfullyutilized in so-called "continuous" reforming systems (i.e. reforming forperiods of about 15 to about 200 or more barrels of charge per pound ofcatalyst without regeneration) with conventional platinum-rheniumcatalyst systems. In other words, the attenuated superactivemultimetallic catalyst of the present invention allowed the operation ofa continuous reforming system to be conducted at lower pressure (i.e.100 to about 350 psig.) for about the same or better catalyst cycle lifebefore regeneration as has been heretofore realized with conventionalplatinum-rhenium catalysts at higher pressure (i.e. 300 to 600 psig.).

The temperature required for reforming with the instant catalyst ismarkedly lower than that required for a similar reforming operationusing a high quality platinum-rhenium catalyst of the prior art. Thissignificant and desirable feature of the present invention is aconsequence of the superior activity of the attenuated superactivepyrolyzed multimetallic catalyst of the present invention for theoctane-upgrading reactions that are preferably induced in a typicalreforming operation. Hence, the present invention requires a temperaturein the range of from about 775° F. to about 1100° F. and preferablyabout 850° F. to about 1050° F. As is well known to those skilled in thecontinuous reforming art, the initial selection of the temperaturewithin this broad range is made primarily as a function of the desiredoctane of the product reformate considering the characteristics of thecharge stock and of the catalyst. Ordinarily, the temperature then isthereafter slowly increased during the run to compensate for theinevitable deactivation that occurs to provide a constant octaneproduct. Due to the outstanding initial activity of the catalyst of thepresent invention, not only is the initial temperature requirementlower, but also the average temperature requirement used to maintain aconstant octane product is, for the instant catalyst system,significantly better than for an equivalent operation with a highlyquality platinum-rhenium catalyst system of the prior art; for instance,a catalyst prepared in accordance with the teachings of U.S. Pat. No.3,415,737. The superior activity, selectivity and stabilitycharacteristics of the instant catalyst can be utilized in a number ofhighly beneficial ways to enable increased performance of a catalyticreforming process relative to that obtained in a similar operation witha platinum-rhenium catalyst of the prior art, some of these are: (1)Octane number of C₅ + product can be increased without sacrificingaverage C₅ + yield and/or catalyst run length. (2) The duration of theprocess operation (i.e. catalyst run length or cycle life) beforeregeneration becomes necessary can be increased. (3) C₅ + yield can beincreased by lowering average reactor pressure with no change incatalyst run length. (4) Investment costs can be lowered without anysacrifice in cycle life or in C₅ + yield by lowering recycle gasrequirements thereby saving on capital cost for compressor capacity orby lowering initial catalyst loading requirements thereby saving on costof catalyst and on capital cost of the reactors. (5) Throughput can beincreased significantly at no sacrifice in catalyst cycle life or inC₅ + yield if sufficient heater capacity is available.

The reforming embodiment of the present invention also typicallyutilizes sufficient hydrogen to provide an amount of about 1 to about 20moles of hydrogen per mole of hydrocarbon entering the reforming zone,with excellent results being obtained when about 2 to about 6 moles ofhydrogen are used per mole of hydrocarbon. Likewise, the liquid hourlyspace velocity (LHSV) used in reforming is selected from the range ofabout 0.1 to about 10, with a value in the range of about 1 to about 5being preferred. In fact, it is a feature of the present invention thatit allows operations to be conducted at higher LHSV than normally can bestably achieved in a continuous reforming process with a high qualityplatinum-rhenium reforming catalyst of the prior art. This last featureis of immense economic significance because it allows a continuousreforming process to operate at the same throughput level with lesscatalyst inventory or at greatly increased throughput level with thesame catalyst inventory than that heretofore used with conventionalplatinum-rhenium reforming catalyst at no sacrifice in catalyst lifebefore regeneration.

The following examples are given to illustrate further the preparationof the attenuated superactive multimetallic catalytic composite of thepresent invention and the use thereof in the conversion of hydrocarbons.It is understood that the examples are intended to be illustrativerather than restrictive.

EXAMPLE I

A sulfur-free, bismuth- and chloride-containing alumina carrier materialcomprising 1/16 inch spheres was prepared by: forming an aluminumhydroxyl chloride sol by dissolving substantially pure aluminum pelletsin a hydrochloric acid solution, admixing bismuth trichloride with theresulting sol in an amount sufficient to result in a finished catalystcontaining a uniform dispersion of about 0.15 wt. % bismuth, addinghexamethylenetetramine to the resulting bismuth-containing alumina sol,gelling the resulting solution by dropping it into an oil bath to formspherical particles of a bismuth-containing alumina hydrogel, aging andwashing the resulting particles and finally drying and calcining theaged and washed particles to form spherical particles of gamma-aluminacontaining about 0.3 wt. % combined chloride, a uniform dispersion ofabout 0.15 wt. % bismuth in the form of bismuth oxide and/or aluminate.Additional details as to this method of preparing the preferredgamma-alumina carrier material are given in the teachings of U.S. Pat.No. 2,620,314.

An aqueous impregnation solution containing chloroplatinic acid andhydrogen chloride was then prepared. The bismuth-containing aluminacarrier material was thereafter admixed with the impregnation solution.The amount of the metallic reagent contained in this impregnationsolution was calculated to result in a final composite containing, on anelemental basis, about 0.375 wt. % platinum. In order to insure uniformdispersion of the platinum component throughout the carrier material,the amount of hydrogen chloride used in this impregnation solution wasabout 2 wt. % of the alumina particles. This impregnation step wasperformed by adding the carrier material particles to the impregnationmixture with constant agitation. In addition, the volume of the solutionwas approximately the same as the bulk volume of the bismuth-containingalumina carrier material particles so that all of the particles wereimmersed in the impregnation solution. The impregnation mixture wasmaintained in contact with the carrier material particles for a periodof about 1/2 to about 3 hours at a temperature of about 70° F.Thereafter, the temperature of the impregnation mixture was raised toabout 225° F. and the excess solution was evaporated in a period ofabout 1 hour. The resulting dried impregnated particles were thensubjected to an oxidation treatment in a dry air stream at a temperatureof about 975° F. and a GHSV of about 500 hr.⁻¹ for about 1/2 hour. Thisoxidation step step was designed to convert substantially all of theplatinum ingredient to the corresponding platinum oxide form. Theresulting oxidized spheres were subsequently contacted in a halogentreating step with an air stream containing H₂ O and HCl in a mole ratioof about 30:1 for about 2 hours at 975° F. and a GHSV of about 500 hr.⁻¹in order to adjust the halogen content of the catalyst particles to avalue of about 1 wt. %. The halogen-treated spheres were thereaftersubjected to a second oxidation step with a dry air stream at 975° F.and a GHSV of 500 hr.⁻¹ for an additional period of about 1/2 hour.

The resulting oxidized, halogen-treated, platinum-and bismuth-containingcarrier material particles were then subjected to a dry reductiontreatment designed to reduce substantially all of the platinum componentto the elemental state and to maintain a uniform dispersion of thiscomponent in the carrier material. This reduction step was accomplishedby contacting the particles with a hydrocarbon-free, dry hydrogen streamcontaining less than 5 vol. ppm. H₂ O at a temperature of about 1050°F., a pressure slightly above atmospheric, a flow rate of hydrogenthrough the particles corresponding to a GHSV of about 400 hr.⁻¹ and fora period of about one hour.

Rhenium carbonyl complex, Re₂ (CO)₁₀, was thereafter dissolved in ananhydrous acetone solvent in order to prepare the rhenium carbonylsolution which was used as the vehicle for reacting the rhenium carbonylcomplex with the carrier material containing the uniformly dispersedplatinum and bismuth. The amount of this complex used was selected toresult in a finished catalyst containing about 0.375 wt. % rheniumderived from rhenium carbonyl. The resulting rhenium carbonyl solutionwas then contacted under appropriate impregnation conditions with thereduced, platinum- and bismuth-containing alumina carrier materialparticles resulting from the previously described reduction step. Theimpregnation conditions utilized were: a contact time of about one halfto about three hours, a temperature of about 70° F. and a pressure ofabout atmospheric. It is important to note that this impregnation stepwas conducted under a nitrogen blanket so that oxygen was excluded fromthe environment and also this step was performed under anhydrousconditions. Thereafter the acetone solvent was removed under flowingnitrogen at a temperature of about 175° F. for a period of about onehour. The resulting dry rhenium carbonyl-impregnated particles were thensubjected to a pyrolysis step designed to decompose the resultingrhenium carbonyl component. This step involved subjecting the rheniumcarbonyl-impregnated particles to a flowing hydrogen stream at a firsttemperature of about 230° F. for about one half hour at a GHSV of about600 hr.⁻¹ and at atmospheric pressure. Thereafter in the second portionof the pyrolysis step the temperature of the impregnated particles wasraised to about 575° F. for an additional interval of about one houruntil the evolution of CO was no longer evident. The resulting catalystwas then maintained under a nitrogen blanket until it was loaded intothe reactor in the subsequently described reforming test.

A sample of the resulting pyrolyzed rhenium carbonyl, bismuth- andplatinum-containing catalytic composite was analyzed and found tocontain, on an elemental basis, about 0.375 wt. % platinum, about 0.375wt. % rhenium derived from rhenium carbonyl, about 0.15 wt. % bismuthand about 1.0 wt. % chloride. The resulting catalyst is hereinafterreferred to as Catalyst A. For this catalyst the atomic ratio of bismuthto platinum was about 0.37:1 and the atomic ratio of rhenium to platinumwas about 1:1.

EXAMPLE II

In order to compare the attenuated superactive acidic multimetalliccatalytic composite of the present invention with a platinum-rheniumcatalyst system in which all of the rhenium component was derived fromthe pyrolysis of rhenium carbonyl in a manner calculated to bring outthe beneficial interaction of the bismuth component with this uniquecatalyst system, a comparison test was made between the catalyst of thepresent invention prepared in accordance with Example I, Catalyst A, anda control catalyst, Catalyst B, which is not a prior art catalyst systembut is rather my prior invention as fully disclosed in my copendingapplication Ser. No. 833,332 filed Sept. 14, 1977 and now U.S. Pat. No.4,165,276. Catalyst B was manufactured according to the procedure givenin Example I except that a pure alumina carrier material was usedinstead of the bismuth-containing carrier material. This controlcatalyst contained the platinum and rhenium metals in the same amountsas the catalyst of the present invention; that is, the catalystcontained about 0.375 wt. % platinum, about 0.375 wt. % rhenium (derivedfrom pyrolysis of rhenium carbonyl) and about 1.0 wt. % chloride.

These catalysts were then separately subjected to a high stressaccelerated catalytic reforming evaluation test designed to determine ina relatively short period of time their relative activity, selectivity,and stability characteristics in a process for reforming a relativelylow-octane gasoline fraction. In both tests the same charge stock wasutilized and its pertinent characteristics are set forth in Table I.

This accelerated reforming test was specifically designed to determinein a very short period of time whether the catalyst being evaluated hassuperior characteristics for use in a high severity reforming operation.

                  TABLE I                                                         ______________________________________                                        Analysis of Charge Stock                                                      ______________________________________                                        Gravity, API at 60° F.                                                                       59.3                                                    Distillation Profile, °F.                                                Initial Boiling Point                                                                             183                                                        5% Boiling Point   210                                                       10% Boiling Point   218                                                       30% Boiling Point   245                                                       50% Boiling Point   270                                                       70% Boiling Point   301                                                       90% Boiling Point   334                                                       95% Boiling Point   345                                                       End Boiling Point   363                                                     Chloride, wt. ppm.    0.6                                                     Nitrogen, wt. ppm.    0.1                                                     Sulfur, wt. ppm.      0.1                                                     Water, wt. ppm.       7                                                       Octane Number, F-1 clear                                                                            31.2                                                    Paraffins + Naphthenes, vol. %                                                                      90.7                                                    Aromatics, vol. %     9.3                                                     ______________________________________                                    

Each run consisted of a series of evaluation periods of 24 hours, eachof these periods comprises a 12-hour line-out period followed by a12-hour test period during which the C₅ + product reformate from theplant was collected and analyzed. The test runs for the Catalysts A andB were performed at identical conditions which comprises a LHSV of 2.0hr.⁻¹, a pressure of 300 psig., a 3.5:1 gas to oil ratio, and an inletreactor temperature which was continuously adjusted throughout the testin order to achieve and maintain a C₅ + target research octane of 100.

Both test runs were performed in a pilot plant scale reforming unitcomprising a reactor containing a fixed bed of the catalyst undergoingevaluation, a hydrogen separation zone, a debutanizer column, andsuitable heating means, pumping means, condensing means, compressingmeans, and the like conventional equipment. The flow scheme utilized inthis plant involves commingling a hydrogen recycle stream with thecharge stock and heating the resulting mixture to the desired conversiontemperature. The heated mixture is then passed downflow into a reactorcontaining the catalyst undergoing evaluation as a stationary bed. Aneffluent stream is then withdrawn from the bottom of the reactor, cooledto about 55° F. and passed to a gas-liquid separation zone wherein ahydrogen-rich gaseous phase separates from a liquid hydrocarbon phase. Aportion of the gaseous phase is then continuously passed through a highsurface area sodium scrubber and the resulting substantially water-freeand sulfur-free hydrogen-containing gas stream is returned to thereactor in order to supply the hydrogen recycle stream. The excessgaseous phase from the separation zone is recovered as thehydrogen-containing product stream (commonly called "excess recyclegas"). The liquid phase from the separation zone is withdrawn therefromand passed to a debutanizer column wherein light ends (i.e. C₁ to C₄)are taken overhead as debutanizer gas and C₅ + reformate streamrecovered as the principal bottom product.

The results of the separate tests performed on the attenuatedsuperactive catalyst of the present invention, Catalysts A, and thecontrol catalyst, Catalyst B, are presented in FIGS. 1, 2 and 3 as afunction of catalyst life as measure in days on oil. FIG. 1 showsgraphically the relationship between C₅ + yields expressed as liquidvolume percent (LV%) of the charge for each of the catalysts. FIG. 2 onthe other hand plots the observed hydrogen purity in mole percent of therecycle gas stream for each of the catalysts. And finally, FIG. 3 tracksinlet reactor temperature necessary for each catalyst to achieve atarget research octane number of 100.

Referring now to the results of the comparison test presented in FIGS.1, 2 and 3 for Catalysts A and B, it is immediately evident that theattenuated superactive multimetallic catalytic composite of the presentinvention substantially outperformed the platinum-rhenium controlcatalyst in the areas of hydrogen production and average C₅ + yield.Turning to FIG. 1 it can be ascertained that the average C₅ +selectivity for Catalyst A was clearly superior to that exhibited forCatalyst B. The difference in C₅ + yield averaged about 3 vol. % for theduration of the common portion of the test and it is clear evidence thatCatalyst A has much better yield-octane characteristics than Catalyst B.Hydrogen selectivities for these two catalysts are given in FIG. 2 andit is clear from the data that there is a significant increase inhydrogen selectivity that accompanies the advance of the presentinvention; I attribute this increased hydrogen selectivity to themoderating effect of bismuth on the increased metal activity enabled bymy unique platinum-rhenium catalyst system. The data presented in FIG. 3immediately highlights the surprising and significant difference inactivity between the two catalyst systems. From the data presented inFIG. 3 it is clear that Catalyst B was consistently 30° to 40° F. moreactive than the catalyst of the present invention when the two catalystswere run at exactly the same conditions. Use of a bismuth component inthe case of my catalyst system, consequently, provides a convenientmeans to trade-off activity for C₅ + and hydrogen selectivity and allowsmy superactive platinum-rhenium catalyst system to be moderated orattenuated in order to adjust the surprising characteristics of thisunique catalyst system to applications where C₅ + yield and hydrogenproduction are more important than extremely high activity.

In final analysis, it is clear from the data presented in FIGS. 1, 2 and3 for Catalysts A and B that the use of a pyrolyzed rhenium carbonylcomponent to interact with a platinum- and bismuth-containing catalyticcomposite provides an efficient and effective means for significantlypromoting an acidic hydrocarbon conversion catalyst containing aplatinum group metal when it is utilized in a high severity reformingoperation. It is likewise clear from these results that the catalystsystem of the present invention is a difference in kind rather thandegree from the platinum-rhenium, platinum-bismuth andplatinum-rhenium-bismuth catalyst systems of the prior art.

It is intended to cover by the following claims all changes andmodifications of the above disclosure of the present invention whichwould be self-evident to a man of ordinary skill in the hydrocarbonconversion art or in the catalyst formulation art.

I claim as my invention:
 1. A catalytic composite comprising acombination of a catalytically effective amount of a pyrolyzed rheniumcarbonyl component with a porous carrier material containing a uniformdispersion of catalytically effective amounts of a platinum groupcomponent, which is maintained in the elemental metallic state duringthe incorporation of the rhenium carbonyl component, and of a bismuthcomponent.
 2. A catalytic composite as defined in claim 1 wherein theplatinum group component is platinum.
 3. A catalytic composite asdefined in claim 1 wherein the platinum group component is ruthenium. 4.A catalytic composite as defined in claim 1 wherein the platinum groupcomponent is rhodium.
 5. A catalytic composite as defined in claim 1wherein the platinum group component is iridium.
 6. A catalyticcomposite as defined in claim 1 wherein the porous carrier materialcontains a catalytically effective amount of a halogen component.
 7. Acatalytic composite as defined in claim 6 wherein the halogen componentis combined chlorine.
 8. A catalytic composite as defined in claim 1wherein the porous carrier material is a refractory inorganic oxide. 9.A catalytic composite as defined in claim 8 wherein the refractoryinorganic oxide is alumina.
 10. A catalytic composite as defined inclaim 1 wherein the composite contains the components in an amount,calculated on an elemental metallic basis, corresponding to about 0.01to about 2 wt. % platinum group metal, about 0.01 to about 5 wt. %bismuth and about 0.01 to about 5 wt. % rhenium.
 11. A catalyticcomposite as defined in claim 6 wherein the halogen component is presenttherein in an amount sufficient to result in the composite containing,on an elemental basis, about 0.1 to about 3.5 wt. % halogen.
 12. Acatalytic composite as defined in claim 1 wherein substantially all ofthe bismuth component is present in an oxidation state above that of theelemental metal.
 13. A catalytic composite as defined in claim 12wherein substantially all of the bismuth component is present as bismuthoxide or bismuth aluminate or as a mixture thereof.
 14. A catalyticcomposite as defined in claim 1 wherein the metals content thereof isadjusted so that the atomic ratio of bismuth to platinum group metal isabout 0.1:1 to 5:1 and the atomic ratio of rhenium, derived from therhenium carbonyl component, to platinum group metal is about 0.5:1 toabout 10:1.
 15. A catalytic composite as defined in claim 6 wherein thecomposite contains, on an elemental basis, about 0.05 to about 1 wt. %platinum group metal, about 0.05 to about 2 wt. % rhenium, about 0.05 toabout 1 wt. % bismuth and about 0.5 to about 1.5 wt. % halogen.
 16. Acatalytic composite as defined in claim 1 wherein the composite isprepared by the steps of: (a) reacting a rhenium carbonyl complex with aporous carrier material containing a uniform dispersion of a platinumgroup component, maintained in the elemental metallic state, and of abismuth component, and thereafter, (b) subjecting the resulting reactionproduct to pyrolysis conditions selected to decompose substantially allof the resulting rhenium carbonyl component.
 17. A catalytic compositeas defined in claim 16 wherein the pyrolysis step is conducted underanhydrous conditions and in the substantial absence of free oxygen. 18.A catalytic composite comprising the pyrolyzed reaction product formedby reacting a catalytically effective amount of a rhenium carbonylcomplex with a porous carrier material containing a uniform dispersionof catalytically effective amounts of a bismuth component and of aplatinum group component maintained in the elemental metallic state, andthereafter subjecting the resulting reaction product to pyrolysisconditions selected to decompose substantially all of the resultingrhenium carbonyl component.